Structural and mechanistic studies of co-ordination compounds. Part 28. Some octahedral ruthenium complexes of 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradeca-1,3,8,10-tetraene produced by oxidative dehydrogenation reactions

Abstract

Low-spin ruthenium(III) complexes, trans-[RuLCl2]+, where L represents C-meso- and C-rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradecane (L1 and L2 respectively) have been found to undergo an eight-electron aerial oxidative dehydrogenation in ethanolic solution to the corresponding dichloro-complexes with unsaturated macrocycles L3 and L4, where L3 and L4 represent C-meso- and C-rac-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetra-azacyclotetradeca-1,3,8,10- tetraene respectively. A series of dianiono-substituted complexes of the type trans-[RuL3X2]n+ (X = Br, n = 1; and X = I; NCS, or NO2, n = 0) have also been prepared. All these complexes have been characterized by i.r. and n.m.r. spectroscopy to contain two pairs of α-di-imine units in the two five-membered chelate rings of the macrocyclic amine ligands. A mechanism for the oxidative dehydrogenation reaction is suggested. The electronic absorption spectra of these complexes are discussed.